Vehicle tailgate dampener and lift assist system

ABSTRACT

A control mechanism for controlling movement of a vehicle gate between a first and a second position comprises a dampener assembly and a lift assembly that are incorporated within the gate. The dampener assembly has a first component mountable to a vehicle structure and a second component supportable by the vehicle gate mounted for pivotal movement relative to the vehicle structure. The first and second components cooperate to control vehicle gate speed as the vehicle gate is moved from the second position to the first position. The lift assembly includes a spring operatively coupled to the dampener assembly to reduce lifting effort as the vehicle gate is moved from the first position to the second position.

The application is a divisional of U.S. application Ser. No. 10/421,328,U.S. Pat. No. 6,854,781, which was filed on Apr. 23, 2003.

BACKGROUND OF THE INVENTION

This invention relates to a lift assist system for a tailgate of avehicle, such as a pickup truck or sport utility vehicle.

A tailgate for a vehicle, such as a pickup truck or sport utilityvehicle, is typically hinged to a vehicle support or frame member andmay be opened and closed by pivoting the tailgate about its hinge tofacilitate access to a truck bed or passenger compartment. A tailgatemay be very heavy, particularly in the case of sport utility vehicles,because window lift and position control components are often housedwithin the tailgate. As a consequence, some assistance may be necessaryto open and close the tailgate.

Systems do exist that provide lift assistance for the tailgate of thevehicle. Indeed, several known systems employ springs to counterbalancethe weight of the tailgate. These springs are located in the sidewallsof the bed of the vehicle. One such system attaches one end of a cableto a spring in the sidewall of the vehicle and the other end to thetailgate. When the tailgate is lowered, the spring expands. Liftassistance to the tailgate is then provided by the returning spring asthe tailgate is lifted.

Such a system, however, has several drawbacks. The spring force must beclosely balanced with the weight of the tailgate so that a vehicleoccupant may easily close the tailgate. However, as a consequence, verylittle upward lift may cause the tailgate to close quickly.

In addition, a driver of the vehicle may desire to keep the tailgateopen during vehicle operation, so as to accommodate oversized loads thatmay extend beyond the vehicle bed or to allow loading or unloading ofthe vehicle while moving. Due to the counterbalancing effect of thespring, over rough roads, the tailgate may close when the driver prefersit to remain open. The tailgate may also bounce up and down on theseroads more so than without the lift assistance. A fluctuating tailgateplaces stress on the tailgate hinge as well as the lift assist system.

Moreover, it is very difficult to install the spring in the sidewallduring vehicle production. Specifically, the spring must be mounted tothe sidewall during assembly of the vehicle body, which is difficult toaccess because the sidewalls typically form an integral part of thebody. Sidewalls for a sport utility vehicle are especially difficult toaccess because of the integration of the sidewalls with a vehicle roof.Installing a spring inside the sidewall accordingly interferes with theassembly of the vehicle body.

Another option would be to install the assist spring outside thesidewall, which avoids interruption of body assembly. However, thespring is then open to the environment and more susceptible to wear anddamage. Thus, it is preferable to keep the spring housed and protected.

Another disadvantage with existing systems is that when the tailgate isopened, the weight of the tailgate is supported in part by thecompressed spring. This design places significant stress on the springand housing for the spring and requires significant reinforcement. As aresult, installation of the lift system is time consuming and expensive.

A need therefore exists for a tailgate assembly that incorporates a liftassist system without the drawbacks encountered by existing systems.

SUMMARY OF THE INVENTION

The present invention comprises a control mechanism for controllingmovement of a vehicle tailgate between open and closed positions. Incontrast to existing assemblies, the invention combines a dampenerassembly with a lift assembly. The dampener has a first componentmounted to a vehicle structure, such as a vehicle sidewall, and a secondcomponent supported by a tailgate and mounted for pivotal movementrelative to the vehicle structure. The first and second componentscooperate to slow tailgate speed as the tailgate is moved between aclosed position and an open position. The lift assembly includes aspring that is coupled to the dampener assembly to reduce lifting effortas the tailgate is moved from the open position to the closed position.Preferably, the spring and dampener assembly are incorporated into thetailgate.

The spring stores energy when the vehicle tailgate moves toward the openposition and releases energy when the vehicle tailgate moves toward theclosed position. The damper assembly helps slow movement of the tailgateas the tailgate is pivoted from the closed position to the openposition. In this way, the invention prevents the tailgate from closingupon the slightest disturbance or opening too quickly while stillproviding adequate lift assistance.

In one disclosed embodiment, the dampener assembly includes a cable anda piston slidably received within a cylinder. The cable is attached tothe piston by a rod. The rod moves in a linear direction parallel to alateral axis about which the tailgate pivots. A guide is used toredirect the cable to the vehicle structure along a long axis that istransverse to the lateral axis.

As discussed above, the lift spring and related components arepreferably enclosed within the tailgate, which facilitates assemblybecause the tailgate is not an integral part of the vehicle body.Moreover, enclosing the spring and dampener assembly within the tailgateprovides a protected environment. The spring is further protected fromthe environment by being enclosed within the dampening cylinder.

In one disclosed embodiment, a rigid stop is used to prevent a catch onthe cable from moving beyond an end of travel position. The stop ispreferably mounted to the tailgate. The stop and catch cooperate toprevent the piston and the rod from bearing the load of the tailgate andany associated payload weight when in the open position.

A latching device is also preferably incorporated within the controlmechanism. The latching device is movable between a first position inwhich the spring is prohibited from providing lift assistance and asecond position in which the spring is released to provide liftassistance. The latching device prevents an unloaded tailgate frombouncing up and down as the vehicle is driven with the tailgate in theopen position and further prevents the tailgate from inadvertentlyclosing. The latching device is preferably actuated by the tailgatelatch handle.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows:

FIG. 1 illustrates a side view of a vehicle and a tailgate in an openposition.

FIG. 2 illustrates a side view of the vehicle and the tailgate of FIG. 1with the tailgate in a closed position.

FIG. 3 illustrates an overhead view of the inventive lift assembly,including cable stop, catch, decoupling device, and dampener with thetailgate in the open position of FIG. 1.

FIG. 4 illustrates the lift assistance device of FIG. 3 in its retractedposition with the tailgate closed.

FIG. 5 shows a piston of the lift assistance device with the rodcompressed in the cylinder.

FIG. 6 shows the piston of FIG. 5 with the rod extended from thecylinder.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 show a side view of tailgate assembly 10 for vehicle body18. The tailgate assembly 10 comprises tailgate 14 attached to vehiclebody 18 with a hinge 16. In FIG. 1, tailgate 14 pivots about hinge 16 ina direction indicated by arrow A to closed position 21 (see FIG. 2)while in FIG. 2, tailgate 14 pivots in a direction indicated by arrow Bto open position 15 (see FIG. 1). Although tailgate 14 is shown here aspart of a pickup truck, tailgate 14 may also be used with othervehicles, such as a sport utility vehicle.

As shown in FIG. 3, tailgate assembly 10 employs a spring 22 to providelift assistance to tailgate 14 and a dampener 101 to control the openingspeed of the tailgate 14. The dampener 101 comprises a piston andcylinder assembly that utilizes a dampening effect to reduce the speedat which the tailgate 14 opens. This prevents a heavy tailgate fromopening too quickly. Spring 22 is housed within cylinder 54 between aspring retainer 55 and a first piston 58. Of course, spring 22 may alsobe mounted outside of cylinder 54 as well. The spring retainer 55 isfixed within cylinder 54, while the first piston 58 is free to moveaxially within cylinder 54. Moreover, the first piston 58 is attached toa rod 62 such that when rod 62 extends in a linear direction indicatedby arrow C out of cylinder 54, the first piston 58 compresses spring 22to store energy for lift assistance. Spring 22 decompresses to releaseenergy for lift assistance when rod 62 moves in a direction indicated byarrow D as shown in FIG. 4.

Hydraulic fluid may be provided within cylinder 54 to dampen movement ofrod 62 from its extended and retracted position. While cylinder 54 isshown here as a hydraulic cylinder, other dampeners, such as a pneumaticdampener, may be employed. The invention is not limited to anyparticular type of dampener.

FIGS. 5 and 6 show a particular cylinder design for a hydraulicdampener. Cylinder 54 has rod 62 disposed therein. Rod 62 may compressinto cylinder 54 as shown in FIG. 5 in the direction of arrow D and mayextend from cylinder 54 as shown in FIG. 6 in the direction of arrow C.Rod 62 is attached to first piston 58. First piston 58 has O-ring 80,valve disc 82 and orifice plate 81. O-ring 80 prevents hydraulic fluidflow around the outside of first piston 58. When rod 62 compresseswithin cylinder 54, O-ring 80 and valve disc 82 are forced away fromorifice plate 81, thereby producing a large non-restrictive flow path 79for hydraulic fluid 77. At extension, friction on O-ring 80 forces valvedisc 82 against the coined orifice plate 81 to restrict flow path 79thereby slowing down the motion of rod 62 during extension, such as whentailgate 14 is opened along the direction of arrow B (see FIG. 2).

As shown in FIGS. 3 and 4, a second piston 56 and a second spring 57 arealso disposed within cylinder 54 and serve to control hydraulic fluidpressure within cylinder 54. The second piston 56 is located near oneend 63 of cylinder 54 and is spaced apart from the first piston 58 andspring retainer 55. While hydraulic fluid fills cylinder 54 between therod seal 53 and the second piston 56, no hydraulic fluid fills cylinder54 between the second piston 56 and end 63. Instead, the second spring57 extends between the second piston 56 and end 63. The second spring 57exerts force on the second piston 56, which, in turn, exerts pressure onhydraulic fluid between the rod seal 53 and the second piston 56. Thispressure helps prevent cavitation of the hydraulic fluid 77 as it passesthrough the orifice of orifice plate 81 when the first piston 58 movesin a direction indicated by arrow C. The second piston 56 is free tomove axially in cylinder 54 in relation to the movement of rod 62. Asrod 62 moves in direction C, second piston 56 moves in direction C, andlikewise for direction D. Hydraulic fluid 77 is incompressible,therefore, as rod 62 moves in and out of cylinder 54 the volume itdisplaces must be offset by a like volume from the movement of secondpiston 56 in cylinder 54.

In contrast to existing systems, spring 22 and cylinder 54 are mountedto tailgate 14 at mounting 61. As shown, mounting 61 may comprise apivot that connects cylinder 54 to tailgate 14. The location of spring22 on tailgate 14 greatly simplifies installation of spring 22 to thevehicle, as tailgate 14 is separately installed from vehicle body 18.Moreover, assembly of spring 22 to tailgate 14 does not interfere withthe construction of vehicle body 18. As shown by cutaway in FIG. 3,spring 22, cylinder 54, and other associated components are installedwithin interior 23 of tailgate 14 between a first exterior surface 13 oftailgate 14 and a second exterior surface 19 of tailgate 14. Thus,spring 22 and other components are protected from the environmentwithout having to install them into sidewalls 17 of vehicle body 18.However, although this protected mounting arrangement is a desirablefeature, it is not necessary for the lift assist system to operate.

As shown in FIG. 3, tailgate 14 utilize first cable 26 and second cable27 to control movement of the tailgate 14 and to support the actualweight of the tailgate in addition to any payload positioned on thetailgate when in the open position. Second cable 27 extends fromsidewall 17 to tailgate 14 along longitudinal axis 31 and supports partof the weight of tailgate 14. The other part of the weight of tailgate14 is supported by first cable 26. First cable 26 and second cable 27are attached at side walls 17 at attachment points 85 as shown in FIGS.1 and 3. The connections 86 used at attachment points 85 are thestandard types used in conventional pickup trucks for easy removal oftailgate 14. The installation of spring 22 and dampener 101 to tailgate14 facilitates the removal of tailgate 14 in the conventional manner.

First cable 26 extends from sidewall 17 along longitudinal axis 31 topulley 66. Pulley 66 directs cable 26 from a lateral axis 30 to alongitudinal axis 31 that is transverse to lateral axis 30. In this way,pulley 66 permits spring 22 and dampener 101 to extend and compressalong lateral axis 30, rather than along longitudinal axis 31, therebyallowing storage of spring 22 and dampener 101 in tailgate 14.

First cable 26 serves as a draw cable to draw tailgate 14 to sidewalls17 of vehicle body 18 as spring 22 decompresses (see FIG. 4) when thetailgate 14 is moved toward the closed position 21 (see FIG. 2). In thisway, spring 22 provides lift assistance to tailgate 14. A catch 34 isattached to rod 62. When tailgate 14 moves to open position 15, as shownin FIGS. 1 and 3, first cable 26 pulls catch 34, rod 62 and first piston58 along arrow C, thereby compressing spring 22 (see Figure 3). Thecompression of spring 22 slows movement of tailgate 14 to open position15. The dampening effect of dampener 101 acts to slow movement oftailgate 14 by slowing movement of first piston 58 and consequently rod62.

Cable stop 38 is mounted within the interior 23 of tailgate 14 and isused to stop movement of first cable 26 and catch 34 along lateral axis30 as tailgate 14 is extended to open position 15. In so doing, cablestop 38 prevents a significant portion of weight of tailgate 14 and anyassociated payload from being exerted on the dampener 101 and spring 22.The second cable 27 is used to support these heavy loads.

In addition, when catch 34 is stopped by cable stop 38 in open position15, latching device 46 may serve to lock catch 34 in place. By lockingcatch 34 in place, spring 22 is held in position and is disengaged fromproviding lift assistance to tailgate 14. Latching device 46 maycomprise a latching pawl that simply blocks movement of catch 34 alongarrow D. Latching device 46 may be linked to a vehicle gate latchactuator 70 so that when vehicle gate latch actuator 70 is actuated,latching device 46 may also be actuated automatically. After tailgate 14is lowered, an operator may toggle vehicle gate latch actuator 70 tolock latching device 46, or latching device 46 may be spring-loaded tolock automatically, and thereby disengage lift assistance by lockingspring 22 into its compressed state. In this way, the lift assistanceprovided by spring 22 is decoupled thereby permitting the full weight oftailgate 14 to keep tailgate 14 in its open position (see FIG. 1) andhelping to avoid the fluttering of tailgate 14 during vehicle operation.When lift assistance is required, door latch 70 may be toggled to unlocklatching device 46 and thereby permit movement of catch 34 in thedirection of arrow D and thereby allow spring 22 to provide liftassistance.

The aforementioned description is exemplary rather that limiting. Manymodifications and variations of the present invention are possible inlight of the above teachings. The preferred embodiments of thisinvention have been disclosed. However, one of ordinary skill in the artwould recognize that certain modifications would come within the scopeof this in invention. Hence, within the scope of the appended claims,the invention may be practiced otherwise than as specifically described.For this reason the following claims should be studied to determine thetrue scope and content of this invention.

1. A vehicle gate assembly for a vehicle, the vehicle gate assemblycomprising: a vehicle gate hingable to a vehicle body for pivotalmovement about a lateral axis between a first position and a secondposition; a spring mountable within said vehicle gate to provide liftassistance as said vehicle gate is moved from said first position tosaid second position: a dampener mountable within said vehicle gate andconnected to said spring to control pivotal speed as said vehicle gateis moved from said second position to said first position; and alatching device having a first latch position in which said spring isprohibited from providing lift assistance and a second latch position inwhich said spring is released to provide lift assistance, wherein saidlatching device is operably coupled to a vehicle gate latch actuator,wherein said dampener comprises a piston disposed within a cylinder andwherein said spring is enclosed within said cylinder for reactionagainst said piston.
 2. The vehicle gate assembly of claim 1 whereinsaid latching device comprises a pawl selectively engageable with a rodto lock said spring.
 3. The vehicle gate assembly of claim 1 including acable having a first end mountable to a vehicle structure and a secondend operably coupled to said piston with a rod.
 4. A vehicle gateassembly for a vehicle, the vehicle gate assembly comprising: a vehiclegate hingable to a vehicle body for pivotal movement about a lateralaxis between a first position and a second position; a spring mountableseparate from said vehicle body to provide lift assistance as saidvehicle gate is moved from said first position to said second position;and a dampener mounted separate from said vehicle body and connected tosaid spring to control pivotal speed as said vehicle gate is moved fromsaid second position to said first position, wherein said dampenercomprises a piston disposed within a cylinder and wherein said spring isenclosed within said cylinder for reaction against said piston.
 5. Thevehicle gate assembly of claim 4 including a cable having a first endmountable to a vehicle structure and a second end operably coupled tosaid piston with a rod.